Taken on Sept. 13, the video shows one of the helicopters slowly spinning into the lake before the aircraft pulled back into the air.
The Navy confirmed that two of its MH-60 Romeo helicopters appeared on the video.
The helicopters were returning to their home base at North Island in San Diego from an air show at Mather Air Force Base in Sacramento. They were supposed to be flying south via Lemoore Naval Air Station in central California, but the video showed them hovering over Lake Tahoe, which is 80 miles to the east of Sacramento and not a normal Navy training area.
Both helicopters sustained damage and made a landing at Lake Tahoe Airport, where the pilots reported the incident to their squadron. No one was injured in the incident.
A repair crew and replacement pilots were sent from San Diego to fly the aircraft home several days after they were repaired.
North Island Naval Air Forces Command spokesman Lt. Aaron Kakiel confirmed that the crews involved in the incident have been grounded while a "mishap aviation board" conducts an investigation. Kakiel said it is standard procedure to ground crews temporarily until an investigation is completed.
MH-60 helicopters typically have a crew of two pilots and one crewman aboard. They are used as anti-submarine platforms that can identify, track and potentially destroy submarines.
The Navy won't specify the damage cost to each aircraft other than to say the typical cost range for what is called a "Class C mishap" is between $50,000 and $500,000.
Of the incident itself, Kakiel said both helicopters "settled with power into Lake Tahoe while attempting to go into a hover."
The term "settled with power" means the aircraft still had power, he said, but not enough to actually hover.
Both crews were able to recover their altitude and air speed and head to the nearby airport, and they discovered minor damage to the aircraft.
The mishap board is looking into whether Lake Tahoe was a part of the original flight plan, whether the crew flying in accordance with F.A.A regulations for that area and if any military policies or regulations for flying in that area were violated, Kakiel said.
Navy Aware of Lake Tahoe Helicopter Video Posted on YouTube
He added that the Navy is aware of the video posted on YouTube, but is not sure if investigators have contacted the videomakers for access to their raw video or if the makers have been interviewed about what they saw that day.
He noted how the video's posting has led to a lot of speculation about what the helicopters were doing when they dipped into the lake, but said, "We're waiting on what the experts tell us about what actually happened rather than relying on YouTube."
The helicopter crews could face administrative measures or disciplinary action depending on what the investigation finds.
On the YouTube video, the voices of two women can be heard reacting to what they were seeing.
One can be heard saying, "The other one's going to do it," before exclaiming, "Oh my gosh. ... Oh!"
Another voice replies, "They're totally practicing, aren't they?"
The first speaker then says, "I didn't even know it was possible."
The description of the video's contents reads: "It looks like a couple of Navy or Coast Guard helicopters practicing a deep swell water rescue. They dunked both choppers into the water. Amazing bit of flying."
The video itself begins with the description, "Emerald bay, Lake Tahoe, 2 helicopters practicng water 'land/take off' procedure."
Recently, the video's poster provided new comments about the video: "From what I am learning this may have been unauthorized training. Never my intent to get people in trouble. Just thought it was some kind of crazy training/practice maneuver. "